Re: [Patch v3 8/9] KVM: x86/mmu: Make split_shadow_page_cache NUMA aware

From: Vipin Sharma
Date: Wed Dec 28 2022 - 17:10:13 EST

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On Tue, Dec 27, 2022 at 11:43 AM Ben Gardon <bgardon@xxxxxxxxxx> wrote:
>
> On Wed, Dec 21, 2022 at 6:35 PM Vipin Sharma <vipinsh@xxxxxxxxxx> wrote:
> >
> > Make split_shadow_page_cache NUMA aware and allocate page table's pages
> > during the split based on the underlying physical page's NUMA node.
> >
> > Signed-off-by: Vipin Sharma <vipinsh@xxxxxxxxxx>
> > ---
> > arch/x86/include/asm/kvm_host.h | 2 +-
> > arch/x86/kvm/mmu/mmu.c | 50 ++++++++++++++++++---------------
> > 2 files changed, 29 insertions(+), 23 deletions(-)
> >
> > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > index b1f319ad6f89..7b3f36ae37a4 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -1410,7 +1410,7 @@ struct kvm_arch {
> > *
> > * Protected by kvm->slots_lock.
> > */
> > - struct kvm_mmu_memory_cache split_shadow_page_cache;
> > + struct kvm_mmu_memory_cache split_shadow_page_cache[MAX_NUMNODES];
> > struct kvm_mmu_memory_cache split_page_header_cache;
> >
> > /*
> > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> > index 511c6ef265ee..7454bfc49a51 100644
> > --- a/arch/x86/kvm/mmu/mmu.c
> > +++ b/arch/x86/kvm/mmu/mmu.c
> > @@ -6126,7 +6126,7 @@ static void kvm_mmu_invalidate_zap_pages_in_memslot(struct kvm *kvm,
> > int kvm_mmu_init_vm(struct kvm *kvm)
> > {
> > struct kvm_page_track_notifier_node *node = &kvm->arch.mmu_sp_tracker;
> > - int r;
> > + int r, nid;
> >
> > INIT_LIST_HEAD(&kvm->arch.active_mmu_pages);
> > INIT_LIST_HEAD(&kvm->arch.possible_nx_huge_pages);
> > @@ -6145,8 +6145,9 @@ int kvm_mmu_init_vm(struct kvm *kvm)
> > INIT_KVM_MMU_MEMORY_CACHE(&kvm->arch.split_page_header_cache,
> > mmu_page_header_cache, NUMA_NO_NODE);
> >
> > - INIT_KVM_MMU_MEMORY_CACHE(&kvm->arch.split_shadow_page_cache,
> > - NULL, NUMA_NO_NODE);
> > + for_each_node(nid)
>
> Again, assuming no one sets CONFIG_NODE_SHIFT to a ridiculous value,
> it would probably be fine to initialize the entire array here since
> that doesn't take any extra memory and we're not in a super hot path.

This goes through the entire array. I think you are confusing it with
for_each_online_node().

>
> > + INIT_KVM_MMU_MEMORY_CACHE(&kvm->arch.split_shadow_page_cache[nid],
> > + NULL, NUMA_NO_NODE);
> > spin_lock_init(&kvm->arch.split_shadow_page_cache_lock);
> >
> > INIT_KVM_MMU_MEMORY_CACHE(&kvm->arch.split_desc_cache,
> > @@ -6157,10 +6158,13 @@ int kvm_mmu_init_vm(struct kvm *kvm)
> >
> > static void mmu_free_vm_memory_caches(struct kvm *kvm)
> > {
> > + int nid;
> > +
> > kvm_mmu_free_memory_cache(&kvm->arch.split_desc_cache);
> > kvm_mmu_free_memory_cache(&kvm->arch.split_page_header_cache);
> > - mmu_free_sp_memory_cache(&kvm->arch.split_shadow_page_cache,
> > - &kvm->arch.split_shadow_page_cache_lock);
> > + for_each_node(nid)
>
> Again, could just iterate over the whole array here.
>
> > + mmu_free_sp_memory_cache(&kvm->arch.split_shadow_page_cache[nid],
> > + &kvm->arch.split_shadow_page_cache_lock);
> > }
> >
> > void kvm_mmu_uninit_vm(struct kvm *kvm)
> > @@ -6269,7 +6273,7 @@ static inline bool need_topup(struct kvm_mmu_memory_cache *cache, int min)
> > return kvm_mmu_memory_cache_nr_free_objects(cache) < min;
> > }
> >
> > -static bool need_topup_split_caches_or_resched(struct kvm *kvm)
> > +static bool need_topup_split_caches_or_resched(struct kvm *kvm, int nid)
> > {
> > if (need_resched() || rwlock_needbreak(&kvm->mmu_lock))
> > return true;
> > @@ -6281,10 +6285,10 @@ static bool need_topup_split_caches_or_resched(struct kvm *kvm)
> > */
> > return need_topup(&kvm->arch.split_desc_cache, SPLIT_DESC_CACHE_MIN_NR_OBJECTS) ||
> > need_topup(&kvm->arch.split_page_header_cache, 1) ||
> > - need_topup(&kvm->arch.split_shadow_page_cache, 1);
> > + need_topup(&kvm->arch.split_shadow_page_cache[nid], 1);
> > }
> >
> > -static int topup_split_caches(struct kvm *kvm)
> > +static int topup_split_caches(struct kvm *kvm, int nid)
> > {
> > /*
> > * Allocating rmap list entries when splitting huge pages for nested
> > @@ -6314,18 +6318,21 @@ static int topup_split_caches(struct kvm *kvm)
> > if (r)
> > return r;
> >
> > - return mmu_topup_sp_memory_cache(&kvm->arch.split_shadow_page_cache,
> > + return mmu_topup_sp_memory_cache(&kvm->arch.split_shadow_page_cache[nid],
> > &kvm->arch.split_shadow_page_cache_lock,
> > 1);
> > }
> >
> > -static struct kvm_mmu_page *shadow_mmu_get_sp_for_split(struct kvm *kvm, u64 *huge_sptep)
> > +static struct kvm_mmu_page *shadow_mmu_get_sp_for_split(struct kvm *kvm,
> > + u64 *huge_sptep,
> > + u64 huge_spte)
>
> These can go on the same line.

Git diff is showing it weirdly. They are aligned to "struct kvm *kvm"
and both will be on different lines to keep them in the 80 char limit.

>
> > {
> > struct kvm_mmu_page *huge_sp = sptep_to_sp(huge_sptep);
> > struct shadow_page_caches caches = {};
> > union kvm_mmu_page_role role;
> > unsigned int access;
> > gfn_t gfn;
> > + int nid;
> >
> > gfn = kvm_mmu_page_get_gfn(huge_sp, spte_index(huge_sptep));
> > access = kvm_mmu_page_get_access(huge_sp, spte_index(huge_sptep));
> > @@ -6338,9 +6345,11 @@ static struct kvm_mmu_page *shadow_mmu_get_sp_for_split(struct kvm *kvm, u64 *hu
> > */
> > role = kvm_mmu_child_role(huge_sptep, /*direct=*/true, access);
> >
> > + nid = kvm_pfn_to_page_table_nid(spte_to_pfn(huge_spte));
> > +
> > /* Direct SPs do not require a shadowed_info_cache. */
> > caches.page_header_cache = &kvm->arch.split_page_header_cache;
> > - caches.shadow_page_cache = &kvm->arch.split_shadow_page_cache;
> > + caches.shadow_page_cache = &kvm->arch.split_shadow_page_cache[nid];
> > caches.shadow_page_cache_lock = &kvm->arch.split_shadow_page_cache_lock;
> >
> > /* Safe to pass NULL for vCPU since requesting a direct SP. */
> > @@ -6360,7 +6369,7 @@ static void shadow_mmu_split_huge_page(struct kvm *kvm,
> > gfn_t gfn;
> > int index;
> >
> > - sp = shadow_mmu_get_sp_for_split(kvm, huge_sptep);
> > + sp = shadow_mmu_get_sp_for_split(kvm, huge_sptep, huge_spte);
> >
> > for (index = 0; index < SPTE_ENT_PER_PAGE; index++) {
> > sptep = &sp->spt[index];
> > @@ -6398,7 +6407,7 @@ static int shadow_mmu_try_split_huge_page(struct kvm *kvm,
> > u64 *huge_sptep)
> > {
> > struct kvm_mmu_page *huge_sp = sptep_to_sp(huge_sptep);
> > - int level, r = 0;
> > + int level, r = 0, nid;
> > gfn_t gfn;
> > u64 spte;
> >
> > @@ -6406,13 +6415,14 @@ static int shadow_mmu_try_split_huge_page(struct kvm *kvm,
> > gfn = kvm_mmu_page_get_gfn(huge_sp, spte_index(huge_sptep));
> > level = huge_sp->role.level;
> > spte = *huge_sptep;
> > + nid = kvm_pfn_to_page_table_nid(spte_to_pfn(spte));
> >
> > if (kvm_mmu_available_pages(kvm) <= KVM_MIN_FREE_MMU_PAGES) {
> > r = -ENOSPC;
> > goto out;
> > }
> >
> > - if (need_topup_split_caches_or_resched(kvm)) {
> > + if (need_topup_split_caches_or_resched(kvm, nid)) {
> > write_unlock(&kvm->mmu_lock);
> > cond_resched();
> > /*
> > @@ -6420,7 +6430,7 @@ static int shadow_mmu_try_split_huge_page(struct kvm *kvm,
> > * rmap iterator should be restarted because the MMU lock was
> > * dropped.
> > */
> > - r = topup_split_caches(kvm) ?: -EAGAIN;
> > + r = topup_split_caches(kvm, nid) ?: -EAGAIN;
> > write_lock(&kvm->mmu_lock);
> > goto out;
> > }
> > @@ -6709,17 +6719,15 @@ void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm, u64 gen)
> > }
> >
> > static unsigned long mmu_shrink_cache(struct kvm_mmu_memory_cache *cache,
> > - int cache_count,
> > spinlock_t *cache_lock)
> > {
> > unsigned long freed = 0;
> > int nid;
> >
> > spin_lock(cache_lock);
> > - for (nid = 0; nid < cache_count; nid++) {
> > - if (node_online(nid) && cache[nid].nobjs)
> > + for_each_online_node(nid)
> > + if (cache[nid].nobjs)
> > freed += kvm_mmu_empty_memory_cache(&cache[nid]);
> > - }
> > spin_unlock(cache_lock);
> > return freed;
> > }
> > @@ -6741,8 +6749,7 @@ mmu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
> > first_kvm = kvm;
> > list_move_tail(&kvm->vm_list, &vm_list);
> >
> > - freed += mmu_shrink_cache(&kvm->arch.split_shadow_page_cache,
> > - 1,
> > + freed += mmu_shrink_cache(kvm->arch.split_shadow_page_cache,
> > &kvm->arch.split_shadow_page_cache_lock);
> >
> > if (freed >= sc->nr_to_scan)
> > @@ -6750,7 +6757,6 @@ mmu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
> >
> > kvm_for_each_vcpu(i, vcpu, kvm) {
> > freed += mmu_shrink_cache(vcpu->arch.mmu_shadow_page_cache,
> > - MAX_NUMNODES,
> > &vcpu->arch.mmu_shadow_page_cache_lock);
> > }
> >
> > --
> > 2.39.0.314.g84b9a713c41-goog
> >

Next message: Vipin Sharma: "Re: [Patch v3 9/9] KVM: x86/mmu: Reduce default cache size in KVM from 40 to PT64_ROOT_MAX_LEVEL"
Previous message: Vipin Sharma: "Re: [Patch v3 7/9] KVM: x86/mmu: Allocate page table's pages on NUMA node of the underlying pages"
In reply to: Ben Gardon: "Re: [Patch v3 8/9] KVM: x86/mmu: Make split_shadow_page_cache NUMA aware"
Next in thread: David Matlack: "Re: [Patch v3 8/9] KVM: x86/mmu: Make split_shadow_page_cache NUMA aware"
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